Among work of fruit tree cultivating farmhouses, work of picking a bud, picking a flower, and picking a fruit for limiting the number of born fruits, and picking leaves aimed at uniform coloring of fruits are a considerably great burden. For example, in an apple, it is said that a ratio of these works occupied in all work accounts for about a half. Among them, work of picking a bud, picking a flower and picking a fruit is important work greatly acting on fruit quality, but since it is necessary that the work is finished in a predetermined short term, a burden on fruit tree farmhouses is great and, in particular in Japan, there is also a problem of aging in an agricultural population, and labor saving is a great theme. These pickings, bud picking, flower picking and fruit picking, are accepted to be a necessary work not only in apple, but also pear, peach, grape, persimmon, citrus fruits, and the work restricts the number of fruits, promoting enlargement of a fruit and development of a branch leaf. Among them, flower picking is performed not only by a manual working method, scattering of a flower thinning agent has been practiced heretofore.
As a flower thinning agent which has been previously proposed and put into practice, for example, there is a flower thinning agent containing a lime and sulfur mixture as an effective ingredient. However, a lime and sulfur mixture has certain effect, but since it is strongly basic and, at the same time, has a strong offensive smell and may have adverse effect on a living body, workability is deteriorated and handling was problematic such as necessity of taking protecting means with a mask, protecting spectacles, or protecting robe. In addition, since a lime and sulfur mixture is strongly basic, there is a fear that a metal of a scattering equipment is eroded. In order to improve this phenomenon, when an amount of lime is decreased and a pH reaches a neutral region, there is a tendency that medicine damage phenomenon such as discoloration of a leaf becomes intense due to increase in an amount of sulfur, therefore, it is not a preferable method to adjust a pH. Further, in the case of use of the lime and sulfur mixture, when a flower visiting insect such as a honey bee and the like is activated, a bad smell based on sulfur is brought by a honey bee, there is a possibility that quality of a honey is deteriorated and, recently, this has become a problem. Therefore, it is hard to say that use of a lime and sulfur mixture is preferable in a respect of side effect although certain flower thinning effect is recognized.
In addition, in JP-A No. 2000-290103, JP-A No. 2001-206804, and JP-A No. 2001-206805, there is provided a flower thinning agent containing, as an effective ingredient, an organic acid such as organic water-soluble citric acid, gluconic acid, succinic acid, lactic acid, fumaric acid, malic acid, acetic acid, tartaric acid, propionic acid and the like, and an organic acid salt. However, when the aforementioned organic acid and organic acid salt are used, if they are scattered within 1 to a few hours after flowering, certain flower thinning effect is recognized, but since a flower thinning agent is used under natural circumstance, it is extremely difficult to usually spread at aimed timing depending on a difference in a district, a change in weather and air temperature. When spread timing is deflected, since the effect is remarkably decreased, there is a defect that it is difficult to achieve stable flower thinning effect.
Further, in JP-A No. 2000-198704, and JP-A No. 2001-328910, there is provided a flower thinning agent containing an aliphatic organic acid such as itaconic acid and the like as an effective ingredient. However, when a medicine containing an aliphatic organic acid such as itaconic acid as an effective ingredient is used, although certain flower thinning effect is recognized, there is a problem that epinasty phenomenon where a leaf is curled or transiently hung and medicine damage such as browning of a leaf occur, thus, this use can not be said to be so preferable.
In addition, since all of the aforementioned substances are water-soluble substances, a flower thinning agent is easily flown away and, when spread proper term is rainy, there is a problem that flower thinning effect is hardly expected.
In addition, in JP-A No. 55-13233, and JP-A No. 58-157706, there is provided a flower thinning agent containing lecithin, plant sterol and the like as an effective ingredient. However, when lecithin or the like is used alone, certain flower thinning effect is recognized, but since durability of effect is insufficient, it is difficult to obtain sufficient flower thinning effect. The reason is thought as follows: that is, since a tree is grown naturally, there is a difference in strength of tree health in each tree unit and each branch unit. Therefore, it is difficult to completely adjust flowering timing of a flower at a flowering season. For this reason, although effect is recognized in a particular branch, effect is hardly confirmed in another branch in some cases, and, as a result, it is presumed that, when a total of a treating section is averaged, it is difficult to necessarily obtain sufficient flower thinning effect. In addition, when a spread concentration is increased in order to compensate for insufficiency of flower thinning effect, there is a tendency that medicine damage such as browning of a leaf occurs, being not preferable. Further, when the substances are dissolved in water and the like, a flower thinning agent is easily flown away and, in the case where a spread proper term is rainy, there is a problem that flower thinning effect is hardly expected.
In view of such the conditions, the present inventors solve the aforementioned problems, and provide a flower thinning agent which is safe for human health, exhibits high adaptability to spread timing deflection and further exhibits high flower thinning efficiency.